Ch 11: Cell Cycle, Mitosis, and Cancer
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Created by:
kuniyosh on November 6, 2011
Subjects:
General Biology Cellular and Genetics
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60 terms
Terms | Definitions |
|---|---|
 Interphase | Time of the cell cyle during which the cell is not dividing. 3 parts: S phase, G1, G2 |
| Synthesis (S) Phase | Time duringwhich the DNA is being replicated |
| G1 | Busiest time for cell metabolism and growth First gap occurs after M phase but before S phase |
| G2 | Allows the cell to build the protein machinery necessary for mitosis Second gap represents period when chromosome replication is complete but mitosis has not yet begun |
| M Phase | The phase of cell cycle in which cell division occurs. Occurs in either Meiosis or Mitosis |
| Meiosis | Form of cell division that occurs only in reproductive cells, and results in cells that have half the chromosomes of the parent cell |
| Mitosis | Cell division that happens in somatic (non-gamete) cells, generating daughter cells that are genetically identical to the parent cell -coined by Walter Flemming |
| All cells do not divide at same rate | -Nondividing cells stay in a G1 like phase called G0 indefinitely -Other cells divide only when triggered by external cues |
| Cyclin/cdks | -Switches that push a cell from one cell-cycle phase to the next -cell fusion experiment demonstrate existence of cell cycle switches -Experiments use frog eggs (oocytes) identified the first cell cycle switch by injecting cytoplasm from frog eggs in M phase into a cell in G2, the G2 phase eggs entered M phase --showed that some molecular signal in cytoplasm that initiated mitosis |
| Mitosis Promoting Factor | -Molecular signal in cytoplasm that initiated mitosis -Comprised of two polypeptide subunits --Cdk --cyclin -When cyclin levels are high, cyclin binds with cdk to form active MPF -Activated MPF phosphorylates proteins that are involved in mitosis -Different sets of cyclin and Cdks are involved at each cell cycle transition |
| Cdk (cyclin-dependent kinase) | Polypeptide that can activate and inactivate other proteins by phosphorylation. Expressed at constant levels throughout the cell cycle |
| Cyclin | Subunit whose concentration fluctuates throughout the cell cycle. |
| Cell Cycle Checkpoints | Regulate cyclin/cdk activity -G1 checkpoint -G2 checkpoint -Metaphase checkpoint |
| G1 Checkpoint | Ensures that each cell is large enough to divide that enough nutrients are available to support the resulting daughter cells and that the DNA is not damaged |
| G2 Checkpoint | Ensures that DNA replication in S phase has been completed successfully |
| Metaphase Checkpoint | Ensures that all of the chromosomes are attached to the mitotic spindle |
| Cancer | General term for disease caused by cells that divide in uncontrolled fashion, invade nearby tissues and spread to other sites in body Loss of cell cycle regulation -Involve uncontrolled cell growth that results in formation of a mass of a cell called a tumor. All cancers share some common properties -Result of failed cell-cycle checkpoints -G1 checkpoint does not work properly. Leaves based on growth factors signalling Ex. retinoblastoma (Rb) and p53 |
| Growth Factors | Intercellular signals that can trigger cells to pass the G1 checkpoint |
| Mitosis Stages | -Prophase -Prometaphase -Metaphase -Anaphase -Telophase and Cytokinesis |
| Prophase | DNA gets "packaged" and ready for movement -DNA is complexed with proteins (histones) into chromatin -Chromatin condenses --Chromatids are joined at centromere to form sister chromatids -Mitotic spindle is built |
| Chromatin | Formed by DNA is complexed with proteins (histones) |
| Chromatid | Each replicated chromosome |
| Sister Chromatids | Chromatids from the same chromosome |
| Prometaphase | -Nuclear envelope breaks down -Spindle fibers from each centrosome attach to one of a pair of sister chromatids at the kinetochore -Centrosomes begin moving to opposite poles of the cell -Spindle fibers attached to kinetochores begin to move the chromosomes to the middle of the cell |
| Metaphase | The chromosomes become lined up at the metaphase plate |
| Anaphase | Separating the duplicated chromosomes -Spindle fibers attached to kinetochores shorten, pulling sister chromatids apart -Spindle fibers that are not attached to kinetochores begin to push against each other via motor proteins that connect them, causing the poles of the cell to be separated even more -Eventually, the chromatids are pulled to opposite poles so that each daughter cell gets identical sets of chromosomes |
| Telophase | Nuclear envelope re-forms and the mitotic spindle disappears |
| Cytokinesis | Cytoplasmic division and the formation of two daughter cells -In animals a cleavage furrow forms between the two new nuclei --this is made from a ring of actin and myosin microfibrils that surround the inside circumference of the cell --microfilaments contract, causing the cell membrane to constrict and pinch the cell in two -In plants cell plate forms --vesicles from golgi apparatus carrying cell-wall material migrate to the middle of the cell between the two nuew nuclei --vesicles build up and fuse, forming a new cell membrane and cell wall dividing the two new nuclei |
| Responsibilites of Mitosis and Cytokinesis | Growth Wound repair Reproduction |
| Asexual Reproduction | Produces offspring that are genetically identical to parent |
| Chromosomes | Single, long DNA double helix wrapped around proteins in highly organized manner |
| Gene | Length of DNA that codes for particular protein of RNA found in cells |
| Centromere | Two chromatids are joined together along entire length as well in specialized region of chromosome |
| Gap Phases | Provide time for cell to grow and synthesize enough organelles |
| Histones | Eukaryotic chromosomes consist of DNA associated with globular proteins |
| Spindle Apparatus | Structure produces mechanical forces that pull chromosomes to poles of cells during mitosis and push poles of cell away from each other -consists of microtubules |
| Polar Microtubules | Extend from spindle and overlap one another in middle of cell |
| Kinetochore Microtubules | Attach to chromosomes to pull them to opposite poles during metaphase -Scientists shown fluorescent light and saw darkened region and found it remained stationary and they get shortened between darkened region and kintechore -During anaphase they shorten due to tubulin subunits are lost from plus end |
| Kinetochore | Attachment between kinetochore microtubules and each chromatid -located at centromere region of chromosomes -each chromosome has two- one one each side |
| Metaphase Plate | When metaphase ends, chromosomes line up along imaginary plane |
| Cell Plate | Vesicles from golgi apparatus are transported to middle of dividing cell in plants -divide two daughter cells with microtubules |
| Cleavage Furrow | In animals, fungi, slimemolds, ring of actin filaments form inside plamsa membrane in plane that bisects cell -myosin- motor proteins binds to actin filaments and with ATP they slide the actin filaments -plasma membrane pinches inward and causes cytokinesis/cell division |
| FtsZ fibers | Form ring in middle of bacteria cells and ring constricts and divides |
| Kinetochore motors | Dyneins and other motor proteins attached to kinetochore's fibrous crown and "walk" down microtubules from plus end to minus end -loss of tubulin on plus end -these proteins walk toward minus end |
| G0 Phase | Non-dividing cells, G1 is stuck, effectively exited cell cycle and sometimes called post-mitotic Ex. Nerve cells and muscle cells |
| Oocyte | cell which is arrested in phase similar to G2 to a mature egg that enters M phase |
| Negative Feedback | Process is slowed or shutdown by one of the products |
| Proteasome | Protein complex attaches small proteins called ubiquitins to cyclin and deactivates MPF |
| Tumor | Cells that keep dividing and form mass of cells without checkpoints |
| p53 | Protein that activates genes that either stop cell cycle until damages can be repaired or cause cell's programmed destruction |
| Apoptosis | Cell's programmed, controlled destruction |
| Tumor Suppressors | Regulatory proteins like p53 |
| Lymphatic Vessels | Collect excess fluid from tissues and return to bloodstream |
| Malignant Tumor | Invasive, one that causes cancer |
| Benign Tumor | Masses of non invasive cells and non cancerous |
| Metastasis | Spreading form primary tumor site, cancer cells can establish secondary tumors elsewhere |
| Social control | cells divide in response to signals from other cells -based on growth factors |
| Platelet Derived Growth Factor (PDGF) | Serum components, released by blood components called platelets which promote blood clotting -Receives signal and cell divide and promotes healing |
| E2F | -Key regulatory protein -Analogous to MPF -Triggers expression of genes required for S phase -Binds to Rb Protein |
| Rb Protein | Tumor Supressor protein, key molecules that enforces G1 checkpoint -High concentrations of growth factors function as social signal to go past G1 and ignore Rb |
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